The Montagut mountain is the northern end of a narrow deposit of sedimentary siliceous rocks called lidites that were formed at the bottom of a cold and very deep sea. They contain still rests of siliceous microfossils and are surrounded by conventional schists, i.e., non-siliceous deposits of the same age, like in Pineda. A more recent plutonic activity led to mineralisation in this area. Lidites and schists are much older than 100 million years, since this is the age of Empordà Pliocene deposits located further to the north, which are not compacted in this extense.
